HCI_VENDOR_DIAG
buf[0] = hci_dev_test_flag(hdev, HCI_VENDOR_DIAG) ? 'Y' : 'N';
hci_dev_set_flag(hdev, HCI_VENDOR_DIAG);
hci_dev_clear_flag(hdev, HCI_VENDOR_DIAG);
hci_dev_test_flag(hdev, HCI_VENDOR_DIAG) && hdev->set_diag)